Originating from the integrated circuit (IC) industry, the field of micro machined sensors and actuators, often referred to as “MEMS” (Micro Electro Mechanical Systems), has grown rapidly and attracted a great deal of interest in recent years. Micromachining and microfabrication advances have allowed for the miniaturization of many types of sensors and actuators. Micro sensor packaging techniques and components, for example, should protect the micro system from its operating environment, while, somewhat in contradiction, enabling interaction with that environment in order to measure or affect the desired physical or chemical parameters.
A number of MEMS-based sensing devices are utilized in various sensor applications. For example, a silicon-based manifold absolute pressure (MAP) sensor can provide an inferred value of air-to-fuel ratio by measuring intake manifold pressure data. Similarly, absolute pressure sensors are required in many applications, including industrial process control, environmental monitoring, and biomedical systems.
Elevated temperature curing of liquid adhesives used to form a sealed cavity causes air expansion within such a cavity, which in turn causes bubbles or leak paths to form. A small vent hole is typically used to allow expanding gas to escape while the liquid seal solidifies. These vent holes assure pressure equalization and minimize undesirable problems, such as primary seal blowout due to excessive pressure. In situations where pressure or a vacuum is generated in the cavity, it is preferable to locate the small vent hole in a location where it can be sealed during a later process.
A vented lid allows the atmosphere inside the sensor to equalize with the outside atmosphere. This allows the equilibrium necessary to maintain a proper atmospheric reference for gauge pressure measurement. In cases where the local environment may include splashing water, oil mist, dust, and other contaminants, the vent must be protected from exposure to these elements. The small vent hole must then also be sealed. If a liquid sealant is used to seal the small vent hole in the lid, similar challenges of expanding or contracting gas from the cavity may necessitate deliberate controls or rework to complete this seal.
In an effort to address the foregoing difficulties, a small vent hole can be placed within the confines of a molded connector, which when interfaced with the final applied mating sealed connector, utilizes the mating connector seal to provide the final cavity seal, and circumvents the need for sealing the small vent hole with additional processes. It is believed that the implementation of such a method as disclosed in greater detail herein can prevent contaminants from reaching the cavity interior.